1 files changed, 241 insertions, 341 deletions

diff --git a/drivers/macintosh/via-macii.c b/drivers/macintosh/via-macii.c
index 1b3bad62a1be..01b8eca7ccd5 100644
--- a/drivers/macintosh/via-macii.c
+++ b/drivers/macintosh/via-macii.c
@@ -12,6 +12,15 @@
  * 1999-08-02 (jmt) - Initial rewrite for Unified ADB.
  * 2000-03-29 Tony Mantler <tonym@mac.linux-m68k.org>
  *                              - Big overhaul, should actually work now.
+ * 2006-12-31 Finn Thain <fthain@telegraphics.com.au> - Another overhaul.
+ *
+ * Suggested reading:
+ *   Inside Macintosh, ch. 5 ADB Manager
+ *   Guide to the Macinstosh Family Hardware, ch. 8 Apple Desktop Bus
+ *   Rockwell R6522 VIA datasheet
+ *
+ * Apple's "ADB Analyzer" bus sniffer is invaluable:
+ *   ftp://ftp.apple.com/developer/Tool_Chest/Devices_-_Hardware/Apple_Desktop_Bus/
  */
  
 #include <stdarg.h>
@@ -26,7 +35,6 @@
 #include <asm/macints.h>
 #include <asm/machw.h>
 #include <asm/mac_via.h>
-#include <asm/io.h>
 #include <asm/system.h>
 
 static volatile unsigned char *via;
@@ -51,9 +59,7 @@ static volatile unsigned char *via;
 #define ANH             (15*RS)         /* A-side data, no handshake */
 
 /* Bits in B data register: all active low */
-#define TREQ            0x08            /* Transfer request (input) */
-#define TACK            0x10            /* Transfer acknowledge (output) */
-#define TIP             0x20            /* Transfer in progress (output) */
+#define CTLR_IRQ        0x08            /* Controller rcv status (input) */
 #define ST_MASK         0x30            /* mask for selecting ADB state bits */
 
 /* Bits in ACR */
@@ -65,8 +71,6 @@ static volatile unsigned char *via;
 #define IER_SET         0x80            /* set bits in IER */
 #define IER_CLR         0               /* clear bits in IER */
 #define SR_INT          0x04            /* Shift register full/empty */
-#define SR_DATA         0x08            /* Shift register data */
-#define SR_CLOCK        0x10            /* Shift register clock */
 
 /* ADB transaction states according to GMHW */
 #define ST_CMD          0x00            /* ADB state: command byte */
@@ -77,7 +81,6 @@ static volatile unsigned char *via;
 static int  macii_init_via(void);
 static void macii_start(void);
 static irqreturn_t macii_interrupt(int irq, void *arg);
-static void macii_retransmit(int);
 static void macii_queue_poll(void);
 
 static int macii_probe(void);
@@ -103,29 +106,37 @@ static enum macii_state {
         sending,
         reading,
         read_done,
-        awaiting_reply
 } macii_state;
 
-static int need_poll;
-static int command_byte;
-static int last_reply;
-static int last_active;
-
-static struct adb_request *current_req;
-static struct adb_request *last_req;
-static struct adb_request *retry_req;
-static unsigned char reply_buf[16];
-static unsigned char *reply_ptr;
-static int reply_len;
-static int reading_reply;
-static int data_index;
-static int first_byte;
-static int prefix_len;
-static int status = ST_IDLE|TREQ;
-static int last_status;
-static int driver_running;
-
-/* debug level 10 required for ADB logging (should be && debug_adb, ideally) */
+static struct adb_request *current_req; /* first request struct in the queue */
+static struct adb_request *last_req;     /* last request struct in the queue */
+static unsigned char reply_buf[16];        /* storage for autopolled replies */
+static unsigned char *reply_ptr;      /* next byte in req->data or reply_buf */
+static int reading_reply;        /* store reply in reply_buf else req->reply */
+static int data_index;      /* index of the next byte to send from req->data */
+static int reply_len; /* number of bytes received in reply_buf or req->reply */
+static int status;          /* VIA's ADB status bits captured upon interrupt */
+static int last_status;              /* status bits as at previous interrupt */
+static int srq_asserted;     /* have to poll for the device that asserted it */
+static int command_byte;         /* the most recent command byte transmitted */
+static int autopoll_devs;      /* bits set are device addresses to be polled */
+
+/* Sanity check for request queue. Doesn't check for cycles. */
+static int request_is_queued(struct adb_request *req) {
+        struct adb_request *cur;
+        unsigned long flags;
+        local_irq_save(flags);
+        cur = current_req;
+        while (cur) {
+                if (cur == req) {
+                        local_irq_restore(flags);
+                        return 1;
+                }
+                cur = cur->next;
+        }
+        local_irq_restore(flags);
+        return 0;
+}
 
 /* Check for MacII style ADB */
 static int macii_probe(void)
@@ -147,15 +158,16 @@ int macii_init(void)
         local_irq_save(flags);
         
         err = macii_init_via();
-        if (err) return err;
+        if (err) goto out;
 
         err = request_irq(IRQ_MAC_ADB, macii_interrupt, IRQ_FLG_LOCK, "ADB",
                           macii_interrupt);
-        if (err) return err;
+        if (err) goto out;
 
         macii_state = idle;
+out:
         local_irq_restore(flags);
-        return 0;
+        return err;
 }
 
 /* initialize the hardware */   
@@ -163,12 +175,12 @@ static int macii_init_via(void)
 {
         unsigned char x;
 
-        /* Set the lines up. We want TREQ as input TACK|TIP as output */
-        via[DIRB] = (via[DIRB] | TACK | TIP) & ~TREQ;
+        /* We want CTLR_IRQ as input and ST_EVEN | ST_ODD as output lines. */
+        via[DIRB] = (via[DIRB] | ST_EVEN | ST_ODD) & ~CTLR_IRQ;
 
         /* Set up state: idle */
         via[B] |= ST_IDLE;
-        last_status = via[B] & (ST_MASK|TREQ);
+        last_status = via[B] & (ST_MASK|CTLR_IRQ);
 
         /* Shift register on input */
         via[ACR] = (via[ACR] & ~SR_CTRL) | SR_EXT;
@@ -179,81 +191,72 @@ static int macii_init_via(void)
         return 0;
 }
 
-/* Send an ADB poll (Talk Register 0 command, tagged on the front of the request queue) */
+/* Send an ADB poll (Talk Register 0 command prepended to the request queue) */
 static void macii_queue_poll(void)
 {
-        static int device = 0;
-        static int in_poll=0;
+        /* No point polling the active device as it will never assert SRQ, so
+         * poll the next device in the autopoll list. This could leave us
+         * stuck in a polling loop if an unprobed device is asserting SRQ.
+         * In theory, that could only happen if a device was plugged in after
+         * probing started. Unplugging it again will break the cycle.
+         * (Simply polling the next higher device often ends up polling almost
+         * every device (after wrapping around), which takes too long.)
+         */
+        int device_mask;
+        int next_device;
         static struct adb_request req;
-        unsigned long flags;
-        
-        if (in_poll) printk("macii_queue_poll: double poll!\n");
-
-        in_poll++;
-        if (++device > 15) device = 1;
-
-        adb_request(&req, NULL, ADBREQ_REPLY|ADBREQ_NOSEND, 1,
-                    ADB_READREG(device, 0));
-
-        local_irq_save(flags);
-
-        req.next = current_req;
-        current_req = &req;
 
-        local_irq_restore(flags);
-        macii_start();
-        in_poll--;
-}
+        if (!autopoll_devs) return;
 
-/* Send an ADB retransmit (Talk, appended to the request queue) */
-static void macii_retransmit(int device)
-{
-        static int in_retransmit = 0;
-        static struct adb_request rt;
-        unsigned long flags;
-        
-        if (in_retransmit) printk("macii_retransmit: double retransmit!\n");
+        device_mask = (1 << (((command_byte & 0xF0) >> 4) + 1)) - 1;
+        if (autopoll_devs & ~device_mask)
+                next_device = ffs(autopoll_devs & ~device_mask) - 1;
+        else
+                next_device = ffs(autopoll_devs) - 1;
 
-        in_retransmit++;
+        BUG_ON(request_is_queued(&req));
 
-        adb_request(&rt, NULL, ADBREQ_REPLY|ADBREQ_NOSEND, 1,
-                    ADB_READREG(device, 0));
+        adb_request(&req, NULL, ADBREQ_NOSEND, 1,
+                    ADB_READREG(next_device, 0));
 
-        local_irq_save(flags);
+        req.sent = 0;
+        req.complete = 0;
+        req.reply_len = 0;
+        req.next = current_req;
 
         if (current_req != NULL) {
-                last_req->next = &rt;
-                last_req = &rt;
+                current_req = &req;
         } else {
-                current_req = &rt;
-                last_req = &rt;
+                current_req = &req;
+                last_req = &req;
         }
-
-        if (macii_state == idle) macii_start();
-
-        local_irq_restore(flags);
-        in_retransmit--;
 }
 
 /* Send an ADB request; if sync, poll out the reply 'till it's done */
 static int macii_send_request(struct adb_request *req, int sync)
 {
-        int i;
+        int err;
+        unsigned long flags;
 
-        i = macii_write(req);
-        if (i) return i;
+        BUG_ON(request_is_queued(req));
 
-        if (sync) {
-                while (!req->complete) macii_poll();
+        local_irq_save(flags);
+        err = macii_write(req);
+        local_irq_restore(flags);
+
+        if (!err && sync) {
+                while (!req->complete) {
+                        macii_poll();
+                }
+                BUG_ON(request_is_queued(req));
         }
-        return 0;
+
+        return err;
 }
 
-/* Send an ADB request */
+/* Send an ADB request (append to request queue) */
 static int macii_write(struct adb_request *req)
 {
-        unsigned long flags;
-
         if (req->nbytes < 2 || req->data[0] != ADB_PACKET || req->nbytes > 15) {
                 req->complete = 1;
                 return -EINVAL;
@@ -264,8 +267,6 @@ static int macii_write(struct adb_request *req)
         req->complete = 0;
         req->reply_len = 0;
 
-        local_irq_save(flags);
-
         if (current_req != NULL) {
                 last_req->next = req;
                 last_req = req;
@@ -274,28 +275,52 @@ static int macii_write(struct adb_request *req)
                 last_req = req;
                 if (macii_state == idle) macii_start();
         }
-
-        local_irq_restore(flags);
         return 0;
 }
 
 /* Start auto-polling */
 static int macii_autopoll(int devs)
 {
-        /* Just ping a random default address */
-        if (!(current_req || retry_req))
-                macii_retransmit( (last_active < 16 && last_active > 0) ? last_active : 3);
-        return 0;
+        static struct adb_request req;
+        unsigned long flags;
+        int err = 0;
+
+        /* bit 1 == device 1, and so on. */
+        autopoll_devs = devs & 0xFFFE;
+
+        if (!autopoll_devs) return 0;
+
+        local_irq_save(flags);
+
+        if (current_req == NULL) {
+                /* Send a Talk Reg 0. The controller will repeatedly transmit
+                 * this as long as it is idle.
+                 */
+                adb_request(&req, NULL, ADBREQ_NOSEND, 1,
+                            ADB_READREG(ffs(autopoll_devs) - 1, 0));
+                err = macii_write(&req);
+        }
+
+        local_irq_restore(flags);
+        return err;
+}
+
+static inline int need_autopoll(void) {
+        /* Was the last command Talk Reg 0
+         * and is the target on the autopoll list?
+         */
+        if ((command_byte & 0x0F) == 0x0C &&
+            ((1 << ((command_byte & 0xF0) >> 4)) & autopoll_devs))
+                return 0;
+        return 1;
 }
 
 /* Prod the chip without interrupts */
 static void macii_poll(void)
 {
-        unsigned long flags;
-
-        local_irq_save(flags);
-        if (via[IFR] & SR_INT) macii_interrupt(0, NULL);
-        local_irq_restore(flags);
+        disable_irq(IRQ_MAC_ADB);
+        macii_interrupt(0, NULL);
+        enable_irq(IRQ_MAC_ADB);
 }
 
 /* Reset the bus */
@@ -303,73 +328,34 @@ static int macii_reset_bus(void)
 {
         static struct adb_request req;
         
+        if (request_is_queued(&req))
+                return 0;
+
         /* Command = 0, Address = ignored */
         adb_request(&req, NULL, 0, 1, ADB_BUSRESET);
 
+        /* Don't want any more requests during the Global Reset low time. */
+        udelay(3000);
+
         return 0;
 }
 
 /* Start sending ADB packet */
 static void macii_start(void)
 {
-        unsigned long flags;
         struct adb_request *req;
 
         req = current_req;
-        if (!req) return;
-        
-        /* assert macii_state == idle */
-        if (macii_state != idle) {
-                printk("macii_start: called while driver busy (%p %x %x)!\n",
-                        req, macii_state, (uint) via1[B] & (ST_MASK|TREQ));
-                return;
-        }
 
-        local_irq_save(flags);
-        
-        /* 
-         * IRQ signaled ?? (means ADB controller wants to send, or might 
-         * be end of packet if we were reading)
-         */
-#if 0 /* FIXME: This is broke broke broke, for some reason */
-        if ((via[B] & TREQ) == 0) {
-                printk("macii_start: weird poll stuff. huh?\n");
-                /*
-                 *      FIXME - we need to restart this on a timer
-                 *      or a collision at boot hangs us.
-                 *      Never set macii_state to idle here, or macii_start 
-                 *      won't be called again from send_request!
-                 *      (need to re-check other cases ...)
-                 */
-                /*
-                 * if the interrupt handler set the need_poll
-                 * flag, it's hopefully a SRQ poll or re-Talk
-                 * so we try to send here anyway
-                 */
-                if (!need_poll) {
-                        if (console_loglevel == 10)
-                                printk("macii_start: device busy - retry %p state %d status %x!\n", 
-                                        req, macii_state,
-                                        (uint) via[B] & (ST_MASK|TREQ));
-                        retry_req = req;
-                        /* set ADB status here ? */
-                        local_irq_restore(flags);
-                        return;
-                } else {
-                        need_poll = 0;
-                }
-        }
-#endif
-        /*
-         * Another retry pending? (sanity check)
+        BUG_ON(req == NULL);
+
+        BUG_ON(macii_state != idle);
+
+        /* Now send it. Be careful though, that first byte of the request
+         * is actually ADB_PACKET; the real data begins at index 1!
+         * And req->nbytes is the number of bytes of real data plus one.
          */
-        if (retry_req) {
-                retry_req = NULL;
-        }
 
-        /* Now send it. Be careful though, that first byte of the request */
-        /* is actually ADB_PACKET; the real data begins at index 1!       */
-        
         /* store command byte */
         command_byte = req->data[1];
         /* Output mode */
@@ -381,115 +367,97 @@ static void macii_start(void)
 
         macii_state = sending;
         data_index = 2;
-
-        local_irq_restore(flags);
 }
 
 /*
- * The notorious ADB interrupt handler - does all of the protocol handling, 
- * except for starting new send operations. Relies heavily on the ADB 
- * controller sending and receiving data, thereby generating SR interrupts
- * for us. This means there has to be always activity on the ADB bus, otherwise
- * the whole process dies and has to be re-kicked by sending TALK requests ...
- * CUDA-based Macs seem to solve this with the autopoll option, for MacII-type
- * ADB the problem isn't solved yet (retransmit of the latest active TALK seems
- * a good choice; either on timeout or on a timer interrupt).
+ * The notorious ADB interrupt handler - does all of the protocol handling.
+ * Relies on the ADB controller sending and receiving data, thereby
+ * generating shift register interrupts (SR_INT) for us. This means there has
+ * to be activity on the ADB bus. The chip will poll to achieve this.
  *
  * The basic ADB state machine was left unchanged from the original MacII code
  * by Alan Cox, which was based on the CUDA driver for PowerMac. 
- * The syntax of the ADB status lines seems to be totally different on MacII, 
- * though. MacII uses the states Command -> Even -> Odd -> Even ->...-> Idle for
- * sending, and Idle -> Even -> Odd -> Even ->...-> Idle for receiving. Start 
- * and end of a receive packet are signaled by asserting /IRQ on the interrupt
- * line. Timeouts are signaled by a sequence of 4 0xFF, with /IRQ asserted on 
- * every other byte. SRQ is probably signaled by 3 or more 0xFF tacked on the 
- * end of a packet. (Thanks to Guido Koerber for eavesdropping on the ADB 
- * protocol with a logic analyzer!!)
- *
- * Note: As of 21/10/97, the MacII ADB part works including timeout detection
- * and retransmit (Talk to the last active device).
+ * The syntax of the ADB status lines is totally different on MacII,
+ * though. MacII uses the states Command -> Even -> Odd -> Even ->...-> Idle
+ * for sending and Idle -> Even -> Odd -> Even ->...-> Idle for receiving.
+ * Start and end of a receive packet are signalled by asserting /IRQ on the
+ * interrupt line (/IRQ means the CTLR_IRQ bit in port B; not to be confused
+ * with the VIA shift register interrupt. /IRQ never actually interrupts the
+ * processor, it's just an ordinary input.)
  */
 static irqreturn_t macii_interrupt(int irq, void *arg)
 {
-        int x, adbdir;
-        unsigned long flags;
+        int x;
+        static int entered;
         struct adb_request *req;
 
-        last_status = status;
-
-        /* prevent races due to SCSI enabling ints */
-        local_irq_save(flags);
-
-        if (driver_running) {
-                local_irq_restore(flags);
-                return IRQ_NONE;
+        if (!arg) {
+                /* Clear the SR IRQ flag when polling. */
+                if (via[IFR] & SR_INT)
+                        via[IFR] = SR_INT;
+                else
+                        return IRQ_NONE;
         }
 
-        driver_running = 1;
-        
-        status = via[B] & (ST_MASK|TREQ);
-        adbdir = via[ACR] & SR_OUT;
+        BUG_ON(entered++);
+
+        last_status = status;
+        status = via[B] & (ST_MASK|CTLR_IRQ);
 
         switch (macii_state) {
                 case idle:
+                        if (reading_reply) {
+                                reply_ptr = current_req->reply;
+                        } else {
+                                BUG_ON(current_req != NULL);
+                                reply_ptr = reply_buf;
+                        }
+
                         x = via[SR];
-                        first_byte = x;
-                        /* set ADB state = even for first data byte */
-                        via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
 
-                        reply_buf[0] = first_byte; /* was command_byte?? */
-                        reply_ptr = reply_buf + 1;
-                        reply_len = 1;
-                        prefix_len = 1;
-                        reading_reply = 0;
-                        
-                        macii_state = reading;
-                        break;
+                        if ((status & CTLR_IRQ) && (x == 0xFF)) {
+                                /* Bus timeout without SRQ sequence:
+                                 *     data is "FF" while CTLR_IRQ is "H"
+                                 */
+                                reply_len = 0;
+                                srq_asserted = 0;
+                                macii_state = read_done;
+                        } else {
+                                macii_state = reading;
+                                *reply_ptr = x;
+                                reply_len = 1;
+                        }
 
-                case awaiting_reply:
-                        /* handshake etc. for II ?? */
-                        x = via[SR];
-                        first_byte = x;
                         /* set ADB state = even for first data byte */
                         via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
-
-                        current_req->reply[0] = first_byte;
-                        reply_ptr = current_req->reply + 1;
-                        reply_len = 1;
-                        prefix_len = 1;
-                        reading_reply = 1;
-
-                        macii_state = reading;                  
                         break;
 
                 case sending:
                         req = current_req;
                         if (data_index >= req->nbytes) {
-                                /* print an error message if a listen command has no data */
-                                if (((command_byte & 0x0C) == 0x08)
-                                 /* && (console_loglevel == 10) */
-                                    && (data_index == 2))
-                                        printk("MacII ADB: listen command with no data: %x!\n", 
-                                                command_byte);
-                                /* reset to shift in */
-                                via[ACR] &= ~SR_OUT;
-                                x = via[SR];
-                                /* set ADB state idle - might get SRQ */
-                                via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
-
                                 req->sent = 1;
+                                macii_state = idle;
 
                                 if (req->reply_expected) {
-                                        macii_state = awaiting_reply;
+                                        reading_reply = 1;
                                 } else {
                                         req->complete = 1;
                                         current_req = req->next;
                                         if (req->done) (*req->done)(req);
-                                        macii_state = idle;
-                                        if (current_req || retry_req)
+
+                                        if (current_req)
                                                 macii_start();
                                         else
-                                                macii_retransmit((command_byte & 0xF0) >> 4);
+                                                if (need_autopoll())
+                                                        macii_autopoll(autopoll_devs);
+                                }
+
+                                if (macii_state == idle) {
+                                        /* reset to shift in */
+                                        via[ACR] &= ~SR_OUT;
+                                        x = via[SR];
+                                        /* set ADB state idle - might get SRQ */
+                                        via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
                                 }
                         } else {
                                 via[SR] = req->data[data_index++];
@@ -505,147 +473,79 @@ static irqreturn_t macii_interrupt(int irq, void *arg)
                         break;
 
                 case reading:
+                        x = via[SR];
+                        BUG_ON((status & ST_MASK) == ST_CMD ||
+                               (status & ST_MASK) == ST_IDLE);
+
+                        /* Bus timeout with SRQ sequence:
+                         *     data is "XX FF"      while CTLR_IRQ is "L L"
+                         * End of packet without SRQ sequence:
+                         *     data is "XX...YY 00" while CTLR_IRQ is "L...H L"
+                         * End of packet SRQ sequence:
+                         *     data is "XX...YY 00" while CTLR_IRQ is "L...L L"
+                         * (where XX is the first response byte and
+                         * YY is the last byte of valid response data.)
+                         */
 
-                        /* timeout / SRQ handling for II hw */
-                        if( (first_byte == 0xFF && (reply_len-prefix_len)==2 
-                             && memcmp(reply_ptr-2,"\xFF\xFF",2)==0) || 
-                            ((reply_len-prefix_len)==3 
-                             && memcmp(reply_ptr-3,"\xFF\xFF\xFF",3)==0))
-                        {
-                                /*
-                                 * possible timeout (in fact, most probably a 
-                                 * timeout, since SRQ can't be signaled without
-                                 * transfer on the bus).
-                                 * The last three bytes seen were FF, together 
-                                 * with the starting byte (in case we started
-                                 * on 'idle' or 'awaiting_reply') this probably
-                                 * makes four. So this is mostl likely #5!
-                                 * The timeout signal is a pattern 1 0 1 0 0..
-                                 * on /INT, meaning we missed it :-(
-                                 */
-                                x = via[SR];
-                                if (x != 0xFF) printk("MacII ADB: mistaken timeout/SRQ!\n");
-
-                                if ((status & TREQ) == (last_status & TREQ)) {
-                                        /* Not a timeout. Unsolicited SRQ? weird. */
-                                        /* Terminate the SRQ packet and poll */
-                                        need_poll = 1;
+                        srq_asserted = 0;
+                        if (!(status & CTLR_IRQ)) {
+                                if (x == 0xFF) {
+                                        if (!(last_status & CTLR_IRQ)) {
+                                                macii_state = read_done;
+                                                reply_len = 0;
+                                                srq_asserted = 1;
+                                        }
+                                } else if (x == 0x00) {
+                                        macii_state = read_done;
+                                        if (!(last_status & CTLR_IRQ))
+                                                srq_asserted = 1;
                                 }
-                                /* There's no packet to get, so reply is blank */
-                                via[B] ^= ST_MASK;
-                                reply_ptr -= (reply_len-prefix_len);
-                                reply_len = prefix_len;
-                                macii_state = read_done;
-                                break;
-                        } /* end timeout / SRQ handling for II hw. */
-
-                        if((reply_len-prefix_len)>3
-                                && memcmp(reply_ptr-3,"\xFF\xFF\xFF",3)==0)
-                        {
-                                /* SRQ tacked on data packet */
-                                /* Terminate the packet (SRQ never ends) */
-                                x = via[SR];
-                                macii_state = read_done;
-                                reply_len -= 3;
-                                reply_ptr -= 3;
-                                need_poll = 1;
-                                /* need to continue; next byte not seen else */
-                        } else {
-                                /* Sanity check */
-                                if (reply_len > 15) reply_len = 0;
-                                /* read byte */
-                                x = via[SR];
-                                *reply_ptr = x;
+                        }
+
+                        if (macii_state == reading) {
+                                BUG_ON(reply_len > 15);
                                 reply_ptr++;
+                                *reply_ptr = x;
                                 reply_len++;
                         }
-                        /* The usual handshake ... */
-
-                        /*
-                         * NetBSD hints that the next to last byte 
-                         * is sent with IRQ !! 
-                         * Guido found out it's the last one (0x0),
-                         * but IRQ should be asserted already.
-                         * Problem with timeout detection: First
-                         * transition to /IRQ might be second 
-                         * byte of timeout packet! 
-                         * Timeouts are signaled by 4x FF.
-                         */
-                        if (((status & TREQ) == 0) && (x == 0x00)) { /* != 0xFF */
-                                /* invert state bits, toggle ODD/EVEN */
-                                via[B] ^= ST_MASK;
 
-                                /* adjust packet length */
-                                reply_len--;
-                                reply_ptr--;
-                                macii_state = read_done;
-                        } else {
-                                /* not caught: ST_CMD */
-                                /* required for re-entry 'reading'! */
-                                if ((status & ST_MASK) == ST_IDLE) {
-                                        /* (in)sanity check - set even */
-                                        via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
-                                } else {
-                                        /* invert state bits */
-                                        via[B] ^= ST_MASK;
-                                }
-                        }
+                        /* invert state bits, toggle ODD/EVEN */
+                        via[B] ^= ST_MASK;
                         break;
 
                 case read_done:
                         x = via[SR];
+
                         if (reading_reply) {
+                                reading_reply = 0;
                                 req = current_req;
-                                req->reply_len = reply_ptr - req->reply;
+                                req->reply_len = reply_len;
                                 req->complete = 1;
                                 current_req = req->next;
                                 if (req->done) (*req->done)(req);
-                        } else {
-                                adb_input(reply_buf, reply_ptr - reply_buf, 0);
-                        }
+                        } else if (reply_len && autopoll_devs)
+                                adb_input(reply_buf, reply_len, 0);
 
-                        /*
-                         * remember this device ID; it's the latest we got a 
-                         * reply from!
-                         */
-                        last_reply = command_byte;
-                        last_active = (command_byte & 0xF0) >> 4;
+                        macii_state = idle;
 
                         /* SRQ seen before, initiate poll now */
-                        if (need_poll) {
-                                macii_state = idle;
+                        if (srq_asserted)
                                 macii_queue_poll();
-                                need_poll = 0;
-                                break;
-                        }
-                        
-                        /* set ADB state to idle */
-                        via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
-                        
-                        /* /IRQ seen, so the ADB controller has data for us */
-                        if ((via[B] & TREQ) != 0) {
-                                macii_state = reading;
 
-                                reply_buf[0] = command_byte;
-                                reply_ptr = reply_buf + 1;
-                                reply_len = 1;
-                                prefix_len = 1;
-                                reading_reply = 0;
-                        } else {
-                                /* no IRQ, send next packet or wait */
-                                macii_state = idle;
-                                if (current_req)
-                                        macii_start();
-                                else
-                                        macii_retransmit(last_active);
-                        }
+                        if (current_req)
+                                macii_start();
+                        else
+                                if (need_autopoll())
+                                        macii_autopoll(autopoll_devs);
+
+                        if (macii_state == idle)
+                                via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
                         break;
 
                 default:
                 break;
         }
-        /* reset mutex and interrupts */
-        driver_running = 0;
-        local_irq_restore(flags);
+
+        entered--;
         return IRQ_HANDLED;
 }